Cutter bits with radially extendable cutter elements

ABSTRACT

A cutter for enlarging a hole in clay, soil, rock or the like comprising a use means which can be moved from an out of use position to allow removal from the hole or to an in use position in which rotation of the cutter causes undercutting or enlargement of the hole.

United States Patent lnventor Allan Richard Hilton Westhoughton, England Appl. No. 7,389

Filed Jan. 29, 1970 Patented Aug. 10, 1971 Assignee Navenhy Limited Bolten, Laneasllire, England Priority June 14, 1967, Oct. 9, 1967 Great Britain 27453167 and 46093167 Continuation of application Ser. No. 736,371, Jane 12, 1968, now abandoned.

CUTTER BITS WITH RADIALLY EXTENDABLE cum: ELEMENTS 6 Claims, 8 Drawing Figs.

u.s. CI. 175/285 1m. (:1 E2lb 9/26 1 16111 61 Search l75/284, 285, 269; 61/5368, 53.6

[56] References Cited UNITED STATES PATENTS 1,269,449 6/1918 Hughes 175/269 X 1,498,463 6/1924 McClosky 175/285 2,176,410 10/1939 Ruddell 175/285 2,450,223 9/1948 Barbour 175/285 2,847,189 8/1958 Shook 175/285 3,114,245 12/1963 Jennings 61/5368 X 3,359,742 12/1967 Blatter 61/5168 X 3,379,266 4/1968 Fletcher 175/285 3,391,543 7/1968 Sweeney 61/53.68 X

Primary Examiner-James A. Leppink Attorney-Holman and Stern ABSTRACT: A cutter for enlarging a hole in clay, soil, rock or the like comprising a use means which can be moved from an out of use position to allow removal from the hole or to an in use position in which rotation of the cutter causes undercutting or enlargement of the hole.

PATENTED AUG 1 0 p97: 3598198 sum 2 OF 2 //VV[/V70P 2L). LAN RICHARD HILTON CUTTER BITS WITH RADIALLY EXTENDABLE CUTTER ELEMENTS This application is a continuation of application Ser. No. 736,371 filed June I2, 1968, now abandoned.

This invention relates to cutter bits for forming anchor holes in clay, soil, rock or like strata in order to provide for anchorage for structures such as pilings, walls and pillars, and methods of anchoring suchstructures.

An object of the present invention is to provide a cutter bit for undercutting or enlarging holes and also to provide a method of anchoring a retaining structure which is efi'ective in a wide variety of strata conditions using such a cutter bit.

According to one aspect of the present invention, there is provided a cutter bit for enlarging a hole in clay, soil, rock or like material comprising cutter means, and means on the cutter bit adapted to move the cutter means from an inoperative position in which the cutter bit can be removed from the hole to an operative position in which rotation of the cutter bit causes the cutter means to undercut or enlarge the hole.

Advantageously, the means adapted to move the cutter means includes a pair of relatively movable parts to which the cutter means are attached in such a manner that, by relative movement of the parts, the cutter means can be moved from its inoperative position in which it lies along the relatively movable parts to an operative position in which it projects laterally away from the relatively movable parts.

Preferably, one of the relatively movable parts is an apertured tube, and the other relatively movable part is a bar slidable within the tube, with the cutter means being pivotably attached to the tube to be capable of movement, upon movement of the bar relative to the tube, between an inoperative position in which the cutter means lies within a tube and the operative position in which the cutter means extends from the apertured tube, whereby, on rotation of the tube, the cutter means is rotated to undercut or enlarge the hole,

According to another aspect of the present invention, there is provided a method of anchoring a structure which retains a mass such as soil, clay, rock or the like comprising the steps of forming an elongated hole in the mass, passing an anchor shoe, block or fabrication along the hole to a position in which the anchor shoe or the like lies beyond the predetermined plane of rupture of the mass, the anchor shoe or the like having one or more covered rods or cables secured thereto for attachment to the retaining structure, passing a grout along the hole to form a securement for the anchor shoe or the like prior or subsequent to the passage of the latter along the elongated hole, filling the hole with grout, with the covering on said one or more rods or cables being of the type which does not bond with the grout so as to allow movement of the rods or cables relative thereto and attaching the one or more rods or cables to the retaining structure.

Preferably, before the anchor shoe or the like is passed along the hole, the hole is undercut using a cutter bit as defined above.

Embodiments of the present invention will now be described, by way of example with reference to the accompanying drawings in which:

FIG. I is a schematic side view of a hydraulically actuated cutter bit according to the present invention.

FIG. 2 is a longitudinal sectional view of part of a cutter bit suitable for hydraulic actuation as above, or mechanical actuation by the mechanisms shown in FIGS.

FIG. 3 is a longitudinal sectional view of the hydraulic actuating parts of the cutter bit shown in FIG. 1, suitable for actuating the cutter bit shown in FIG. 2.

FIG. 4 is a longitudinal sectional view of an actuating head suitable for mechanically actuating the cutter bit shown in FIG. 2.

FIG. 5 is a schematic part longitudinal sectional view of a further cutter bit according to the present invention which is particularly suitable for use in clay-containing strata.

FIG. 6 is a cross-sectional view taken along the line A-A of the cutter bit shown in FIG. 5.

FIG. 7 is a longitudinal sectional view of a mechanism for mechanically operating from the surface a cutter bit of the type shown in FIG. 2, and

FIG. 8 is a schematic view of method of anchoring according to the present invention.

Referring to FIGS. 1, 2 and 3, the cutter bit which is for forming and undercutting or enlarging holes in cohesive soils or rock formations comprises a thick-walled metal tube 1 or circular cross section and into one end of which is screw threaded a cutter 2 for cutting a hole in the soil or rock upon rotation of the tube 1.

Two pairs of diametrically opposed apertures 3 and 4 are formed in the wall of the tube 1, with one pair of apertures 3 being spaced longitudinally from the other pair 4 (see especially FIG. 2).

Within the tube 1 is carried a longitudinally slidable metal bar 5 having an aperture 6 or 7 extending therethrough corresponding to each pair of apertures 3 or 4 in the tube. The hole cutter remote end of each aperture 6 or 7 in thebar 5 is formed with a cam face 8 or 9, respectively. Cutter blades 10 and I] having sharpened cutter edges 12 (only one shown) and profiled follower faces 14 and 15 are located one in each aperture 6 or 7, respectively in the bar 5 with the profiled follower face 14 or 15 lying adjacent the cam face 8 or 9 of the bar 5. Each cutter blade is pivotally mounted through a pin 16 to the wall of the tube 1. The pivot point of one cutter blade is on the opposite side of the tube to that of the other cutter blade and its follower face is profiled in the opposite direction so that upon longitudinal movement of the bar 5 relative to the tube 1, the cam faces 8 and 9 engage their respective follower faces 14 and 15 on the cutter blades and push such faces from an inoperative position within the tube to an operative position in which they extends radially on opposite sides of the tube, with the operative position of the cutter blade 11 being shown in dotted line in FIG. 2. The cutter blades 10 and II are shown in FIG. 2 with alternative profiles. The. amount of movement of the blades is governed by movement of the metal bar 5 and a pin 17 carried by the bar 5 in a curved slot l8 in each cutter blade ensures positive retraction of the cutter blades, and only one such pin I7 and slot I8 is illustrated in FIG. 2.

Referring to FIG. 3, the end of the tube 1 remote from the hole cutter.2 is closed by a hollow member 19 in which is located a hydraulic piston 20 longitudinally slidable relative to the tube 1. The metal bar 5 in the tube 1 is urged against one end of the piston 20 by a spring 21 mounted in the tube 1 at the end of the bar 5 opposite from the piston 20. The end of the piston 20 remote from the bar 5 forms one wall of a chamber 22 in the hollow member 19 to which hydraulic fluid can be supplied through a conduit 23 in the hollow member 19. An internally screw-threaded bore 24 is formed in the end of the hollow member 19 remote from the tube and serves to accommodate a screw-threaded end 25 of an arbor 26 (see FIG. 1). The arbor 26 is provided with a conduit 27 which provides communication between the conduit 23 in the hollow member 19 and a conventional external source of hydraulic fluid pressure (not shown). The arbor 26 is also provided with a pair of conduits 28 which connects a convenient external source of pressurized air with a pair of oval air pipes 29 carries in longitudinal recesses in the tube of the cutter bit and leading to the hole cutter 2 for the purpose of clearing the hole cutter 2 during drilling.

In operation, the cutter bit is rotated by the arbor 26 so as to rotate the hole cutter 2 in order to bore a hole in the soil or rock. Compressed air is passed down through the conduits 28 in the arbor and the air pipes 29 so as to prevent the hole cutter 2 from clogging. When the desired depth of hole is reached. drilling is stopped and hydraulic fluid under pressure is passed down into the cutter bit through the conduits 27 and 23 so as to shift the piston 20 and thus the metal bar 5 relative to the tube 1 against the action of the spring 21. Thus, the cutter blades 10 and 11 are pivoted from their inoperative position to a position which which they extends radially from the tube 1. The arbor 26 is rotated and profile enlargement of an anchorage formed by a the hole results. The length of this enlargement may be increased by slowing withdrawing the cutter bit from the bottom of the hole until the desired amount of material has been cut from the wall of the hole by the cutter blades. Then the hydraulic pressure on the piston 20 is released and the bar 5 moves under the action of the spring 21 to withdraw the cutter blades and 11 into the tube 1, and the movement of the cutter blades is being controlled by the pin 17 located in the curved slot 18 in each cutter blade. With the cutter blades in their inoperative position, it is possible to withdraw the cutter bit prior to locating an anchor shoe or the like into the hole and anchoring it into position with cement or other grout.

In a second embodiment of the present invention, the hole cutter on the cutter bit is replaced by a solid head (see FIG. 4) carried on the apertured metal bar 5 through the intermediary ofa ball race 31, thereby dispensing with the hydraulic circuitry. A resilient member 32 is mounted between the tube 1 and an extension 33 of the head 30 so as to urge an annular lip 34 on the extension 33 into engagement with an annular projection 35 on the apertured metal 5. In this way, the metal bar 5 is normally urged by a resilient member 32 into a position in which the cutter blades 10 and 11 are in their inoperative position. In use, the cutter bit attached to the end of the arbor 26, which in this case need not be provided with conduits 27 and 28, is passed down a previously cut hole until the solid head 30 engages with the soil or rock at the bottom of the hole. Pressure on the arbor 26 causes the tube 1 to move relative to the metal bar 5 against the action of the resilient member 32 and causes the cutter blades 10 and 11 to be pivoted into their operative position. The arbor 26 is rotated, while maintaining the pressure thereon, in order to rotate the cutter blades 10 and 11. Thus undercutting of the hole is effected. When it is desired to remove the cutter bit from the hole, the pressure on the arbor 26 is released, and the cutter blades 10 and I] withdraw into the tube I under the action of the resilient member 32. Removal ofthe cutter bit is then possible.

In a further embodiment shown in FIGS. 5 and 6, the profiled cutter blades I0 and II are replaced by a pair of articulated, toothed cutters 37 and 38 extending along the length of the cutter bit. Each cutter 37 or 38 is of arcuate cross section so as to lie close against the tube 1 when in an inopera tive position and is attached it one end by means of a pivot 39 to the tube 1 and at the other end by means ofa pivot 40 to the metal bar 5 which, in this case, is hollow and is splined so that it can be moved longitudinally relative to the tube 1 but is constrained to rotate with the tube 1. The metal bar 5 extends beyond the tube end is provided with a solid head 30 carried thereon through the intermediary of the ball race 31 in a similar manner to that described for the cutter bit shown in FIG. 4.

In operation, the cutter bit, attached to the end of the arbor 26, is passed into a previously bored hole until the solid head 30 contacts the bottom of the hole. Pressure on the arbor 26 causes the tube 1 to be moved relative to the splined metal bar 5, thereby causing the articulated cutters 37 and 38 to be pivoted radially outward into their operative position, with the operative position of the cutter 37 being indicated in dotted line in FIG. 5. The arbor 26 is then rotated in order to rotate the cutters 37 and 38 and at the same time air under pressure is passed down the hollow in the splined metal bar 5 to issue from holes 4| immediately behind the solid head 30 so that the cutters 37 and 38 are prevented from clogging. Thus, the hole is undercut by enlarging the wall of the hole adjacent the base thereof. When it is desired to remove the cutter hit from the hole, the arbor 26 is withdrawn, the tube I moves relative to the splined metal bar 5 and the articulated cutters 37 and 38 pivot back to their inoperative position in which the nest against the tube. This type of cutter bit is especially suitable for undercutting holes in clay strata.

Referring now to FIG. 7, the cutter bit shown in FIG. 2 can be operated by the mechanism which comprises a hollow arbor or drill tube 42 having secured to one end thereof the tube 1 of the cutter bit. To the other end of the hollow arbor or drill tube 42 is attached an output shaft 43 of a known type of drilling machine 44. Thus, rotation of the machine causes rotation of the hollow arbor 42, cutter bit tube 1 and a hole cutter of the type shown in FIG. 1 in order to bore a hole in the soil or rock.

Within the hollow arbor 42 is carried a rod 45 which is lon- In operation, a hole is bored in the soil or rock by rotating the arbor 42, cutter bit and hole cutter by means ofthe drilling machine 44. When the hole has been bored to the required depth, the rod 45 in the arbor 42 is pulled by means of the device for applying a pulling force and the metal bar 5 in the cutter bit slides relative to the tube 1 until the cutter blades extend through the apertures in the cutter bit wall into their operative position as described with reference to FIG. 2. The arbor 42 is rotated and undercutting or enlarging of the hole is effected. Thereafter, the pulling force on the rod 45 is released and the cutter blades retract into the cutter bit tube to allow the cutter bits to be removed from the hole as previously described.

It will be appreciated that the rod may be inserted into the hollow arbor to cooperate with the metal bar of the cutter bit after the hole-boring step has been completed.

It will also be appreciated that more than one rod or one or more wires may be employed, if desired, to operate the metal bar of the cutter bit.

In a further embodiment (not shown), a hydraulic or pneu matic piston and cylinder device is mounted on the cutter bit adjacent each cutter blade and replaced the apertured metal bar as a means for operating the cutter blades. Operation of the piston and cylinder devices cause the cutter blades to move from their inoperative position into their operative position, and a return spring is provided to retract each cutter blade when it is desired to remove the cutter bit from the hole.

It will be appreciated that the cutters may be provided with sharpened edges, teeth, stellite hardening tips or with a cover of a tungsten carbide matrix depending upon the type of strata to be cut.

In place of compressed air, water may be employed for preventing the cutters from clogging. Instead of hydraulic fluid, compressed air may be employed to operate the piston in the first embodiment.

It will be appreciated further than the number and shape of the cutter blades can be varied at will to suit the requirements of the anchorage, and, if desired, a single cutter can be employed.

A cutter bit according to the present invention is particularly suitable for forming an undercut hole in the method of anchoring described hereinafter with reference to FIG. 8.

Referring now to FIG. 8, the method of forming an anchorage for a piling 49 supporting a mass 50 of material of the type wherein a hole drilled in the mass 50 will maintain its diameter for some time, comprises the step of boring a downwardly inclined hole 5|, preferably having a diameter of between 3 and 5 inches, into the mass 50 to extend from a predetermined position 52 related to the piling 49 to a position beyond the predetermined plane of rupture of the mass, and the plane of rupture of the mass 50 is indicated by dotted line 53. The boring tool is then removed from the hole 51 and a multibarbed anchor shoe S4 is passed down the hole 5] until the whole of the anchor shoe lies beyond the plane 53 of rupture of the mass 50. Before being passed down the hole 52, a covered rod 55 is screwed into a screw-threaded bore in the rear end of the shoe, with the rod 55 being ofa predetermined length such that when the anchor shoe 54 is in its correct position, the free end of the rod 55 can be connected with the piling 49. Tin this way, the anchor shoe 54 can be precisely positioned relative to the predetermined plane 53 of rupture of the mass. A rigid grout tube (not shown) is inserted into the hole 52 over the rod 55 and is passed down until it contacts the anchor shoe 54. At the shoe-contacting end of the grout tube is formed a flexible rubber covered spring steel cage (not shown) which, when forced against the anchor shoe 54, splays outwardly to seal the hole around the end of the grout tube. Cement grout 56 under a predetermined pressure is then passed down the tube and surrounds the anchor shoe 54 to locate it firmly within the stable mass of material beyond the plane 53 of rupture. During this stage, the tube is passed against the anchor shoe S4 to maintain the seal. The pressure applied to the cement grout 56 is determined by the physical properties of the material and determines the final shape of the anchorage.

When the pressure on the tube is released, the spring steel cage returns to a position which permits withdrawal of the tube from the hole. During withdrawal of the tube, cement grout is continued to be fed down the tube so as to fill the hole around the covered rod. The covering on the rod is of the type which will not bond with the cement, so that post stressing of the rod is possible. The cement surrounding the rod increases the stability of the mass in the zone supported by the piling. In the case where the mass of material is such that the hole has to be maintained throughout the hole-boring operation, the boring is carried out by a rotary flight auger which is arranged to be equalled or followed by a lining tube it a similar feed rate, with the tube having a head with a cutting edge or suitable inserts and being rotated or oscillated to facilitate passage through the material. When the predetermined depth of hole is reached, the flight auger is withdrawn and the anchor shoe with its associated covered rod is then inserted and the grouting operation commenced.

ln drilling the hole, there may be employed any one of the cutter bits described hereinbefore in order to increase the diameter of the hole at the location where the anchor shoe is to be disposed thus increasing the cross-sectional area of the hole at this location. After this operation, the cutter bit is withdrawn from the hole and the anchor shoe and covered rod or cable are inserted in position and grout fed in prior or subsequent to the shoe insertion.

An alternative method of sealing the end of the grout tube with the hole is by using compounds which are mixed together at the section preceding the anchor shoe and which form a hard synthetic cement to seal the end of the tube with the hole. This method is particularly suited for use in plastic clays, when the grout tube is not removed but remains in the hole throughout the cement-setting period to maintain pressure around the anchor shoe thus countering the flow of such clays.

A further method of sealing the end of the grout tube is effected by means of a spring steel cone on the end of the grout tube, and the cone is arranged to splay outwardly to seal the hole upon application of pressure to the cement grout.

Under certain mass conditions, pressurized feeding of the cement grout is not required and in this case the hole at the end ofthe grout tube need not be sealed, and the cement grout is merely poured down the grout tube to secure the anchor shoe in position.

Alternatively, under similar conditions, synthetic resins can first be fed into the hole and followed by the shoe or fabrication. Movement of the shoe or fabrication results in an intermixing of the resins to form a surrounding mass of synthetic grout.

It will be readily appreciated that one or more covered rods may be employed or alternatively one or more covered cables, depending upon the mass conditions and anchorage requirements.

The rods or cables will be covered by coating or wrapping processes, with the material of the covering always being of a type which does not bond with the surrounding cement so as to allow rod or cable elongation freely is and when required. The thickness and type of the covering is variable according to the purpose of the anchorage, i.e. temporary or permanent,

Dependent upon the conditions, a flexible grout tube may be employed in the place of therigid tube. The anchor shoe may be replaced by a block or fabrication of a form suited to the properties of the mass being retained and the requirements of the anchorage, and the form is indented or shouldered to obtain maximum anchorage strength. The rod or cable may be welded, swaged, cored or so otherwise affixed into the anchor shoe, block or fabrication as to ensure an effective connectron.

It is considered that the method of anchorage according to the present invention has the advantage that a maximum anchorage is obtained due to the design of the anchor shoe, block or fabrication, the position in which it is placed, with the pressure of the cement grout or the shape of the undercut of the hole according to the physical properties of the mass being retained, and the fact that the rods ro cables are free to elongate within the cement in order that poststressing after the ce' ment has set can be applied or allowed so that the cement covering the rods or cables functions as a compression pile which increases the stability of the system.

It will be apparent that any suitable type of grout may be employed in the place of cement grout, for example a synthetic plastic material grout.

I claim:

1. A cutter bit including a tubular body, a bar member snugly and slidably received in said tubular body, said bar member having it least two axially extending slots longitudinally spaced apart, said body having at least two pairs of diametrically opposed, axially extending slots, the pairs of slots in said body registering with said slots in said bar member, and a cutter blade lying within each of said slots in said bar member, each blade having a width not substantially less than the diameter of the outer body whereby the longitudinal side edges of the blades lie within the slots in the tubular body, said blades being pivotally mounted to the tubular body one at one side and the other at the other side thereof, opposed outside side faces of the blades abutting longitudinal side faces of the slots and said blades and slots having complemental means, which coact upon sliding movement of the bar member in one direction, to move the blades from an inoperative position within the tubular body to an operative position in which the blades extend radially on opposite sides of the tubular body.

2. A cutter bit including an outer tubular member, an inner bar member slidably housed within said outer tubular member, an inner bar member slidably housed within said outer tubular member, said inner bar member having at least two apertures diametrically therethrough and elongated in an axial direction, the apertures lying in the same radial plane with one aperture being axially offset from the other, said outer tubular member being provided with at least two pairs of diametrically opposed, axially elongated apertures registering with said apertures in said inner bar member, a cutter blade lying within each of said elongated apertures in said bar member, each blade having a width not substantially less thin the diameter of the outer tubular member, whereby the longitudinal side edges of the blades lie within the apertures in the outer tubular member, and opposed outside side faces of the blades abutting longitudinal side faces of the apertures, one blade being pivotally attached to one side of the outer tubular member adjacent one end of the aperture therein and the other blade being pivotally attached to the other side of the outer tubular member adjacent the corresponding end of the other aperture therein, a cam face, one for each blade, provided at corresponding ends of each of the apertures in the inner bar member which ends are adjacent the pivoted ends of the blades, and a cam follower, engageable by the respective cam face, provided on each blade adjacent its pivot end, whereby upon sliding movement of the inner bar member in one direction relative to the outer tubular member, the cam faces engage the respective cam followers and push the blades from an inoperative position within the outer tubular member to an operative position in which the blades extends radially on opposite sides of the outer tubular member.

3. A cutter bit including a thick-walled outer sleeve, an inner bar member slidably housed therein and capable of axial displacement relative thereto, said inner bar member having at least two slots diametrically therethrough and elongated in the axial direction, said slots being axially offset one from the other, said outer sleeve being provided with at least two pairs of diametrically opposed, axially extending slots respectively registering with said slot in said inner bar member, a cutter blade lying within each slot in said inner bar member, each blade being of a width not substantially less than the outside diameter of the sleeve whereby the longitudinal side edges of each blade lie within the respective slots in said sleeve, with the opposed outside side faces of each blade abutting the lon gitudinal side faces of the slots in the outer sleeve, one blade bein'g"pivotally attached to one side of the outer sleeve adjacent one end of one slot therein and the other blade being pivotally attached to the other side of the outer sleeve adjacent the corresponding end of the other slot therein, a cam face for each blade at the end of the respective slot in the inner bar member adjacent the pivoted end of the blade, and a cam follower provided on each blade adjacent its pivoted end and engageable with a respective cam face whereby upon relative axial displacement of the outer sleeve and the inner bar member, each cam face is engaged by its respective cam follower and the blades are caused to pivot simultaneously radially outwardly.

4. The cutter bit as claimed in claim 1 in which said bar member and cutter blades are provided with complemental means, operative upon movement of the bar member in the opposite direction, to retract the cutter blades into the slots.

5. The cutter bit as claimed in claim 2 in which said inner bar member and cutter blades are provided with complemental means operative, upon movement of the inner bar member in the opposite direction relative to the outer tubular member to retract the cutter blades into the apertures.

6. A cutter bit including a walled outer sleeve having opposite ends, a cutter secured to one end, a bar member mounted within and capable of axial movement relative to the outer sleeve, said bar member being provided with at least two slots diametrically therethrough and elongated in the axial direction, with the slots being axially offset one from the other, said outer sleeve being provided with at least two pairs of diametrically opposed, axially extending slots respectively registering with said slots in the bar member, a cutter blade lying within each slot in the bar member, each blade being ofa width not substantially less than the outside diameter of the sleeve whereby the longitudinal side edges of each blade lie within the respective slots in the sleeve, with the opposed outside side faces of each blade abutting the longitudinal side faces of the slot in the outer sleeve, one blade being pivotally attached to one side of the sleeve adjacent one end of one slot therein and the other blade being pivotally attached to the other side of the sleeve adjacent the corresponding end of the other slot therein, a cam face for each blade at the end of the respective slot in the bar member adjacent the pivoted end of the blade, a cam follower on each blade adjacent its pivoted end and engageable with a respective cam face, a cylinder for the opposite end of the outer sleeve, a piston in the cylinder movable longitudinally relative to the sleeve, spring means within the outer sleeve adjacent said one end thereof urging the bar member against the piston, means to introduce fluid pressure into the cylinder so that the piston displaces the bar member against the action of the spring means in a direction towards said one end of the sleeve whereby each cam face is engaged by its respective cam follower and the blades are caused to pivot simultaneously radially outwardly, each blade having an arcuate slot therein, and two pins extending outwardly from the bar member, with a pin located in each arcuate slot whereby upon cessation of the introduction of fluid pressure into the cylinder, the spring means urges the bar member towards the opposite end of the sleeve and said pins and arcuate slots cooperate to retract blades into the slots in the bar member. 

1. A cutter bit including a tubular body, a bar member snugly and slidably received in said tubular body, said bar member having it least two axially extending slots longitudinally spaced apart, said body having at least two pairs of diametrically opposed, axially extending slots, the pairs of slots in said body registering with said slots in said bar member, and a cutter blade lying within each of said slots in said bar member, each blade having a width not substantially less than the diameter of the outer body whereby the longitudinal side edges of the blades lie within the slots in the tubular body, said blades being pivotally mounted to the tubular body one at one side and the other at the other side thereof, opposed outside side faces of the blades abutting longitudinal side faces of the slots and said blades and slots having complemental means, which coact upon sliding movement of the bar member in one direction, to move the blades from an inoperative position within the tubular body to an operative position in which the blades extend radially on opposite sides of the tubular body.
 2. A cutter bit including an outer tubular member, an inner bar member slidably housed within said outer tubular member, an inner bar member slidably housed within said outer tubular member, said inner bar member having at least two apertures diametrically therethrough and elongated in an axial direction, the apertures lying in the same radial plane with one aperture being axially offset from the other, said outer tubular member being provided with at least two pairs of diametrically opposed, axially elongated apertures registering with said apertures in said inner bar member, a cutter blade lying within each of said elongated apertures in said bar member, each blade having a width not substantially less thin the diameter of the outer tubular member, whereby the longitudinal side edges of the blades lie within the apertures in the outer tubular member, and opposed outside side faces of the blades abutting longitudinal side faces of the apertures, one blade being pivotally attached to one side of the outer tubular member adjacent one end of the aperture therein and the other blade being pivotally attached to the other side of the outer tubular member adjacent the corresponding end of the other aperture therein, a cam face, one for each blade, provided at corresponding ends of each of the apertures in the inner bar member which ends are adjacent the pivoted ends of the blades, and a cam follower, engageable by the respective cam face, provided on each blade adjacent its pivot end, whereby upon sliding movement of the inner bar member in one direction relative to the outer tubular member, the cam faces engage the respective cam followers and push the blades from an inoperative position within the outer tubular member to an operative position in which the blades extends radially on opposite sides of the outer tubular member.
 3. A cutter bit including a thick-walled outer sleeve, an inner bar member slidably housed therein and capable of axial displacement relative thereto, said inner bar member having at least two slots diametrically therethrough and elongated in the axial direction, said slots being axially offset one from the other, said outer sleeve being provided with at least two pairs of diametrically opposed, axially extending slots respectively registering with said slot in said inner bar member, a cutter blade lying within each slot in said inner bar member, each blade being of a width not substantially less than the outside diameter of the sleeve whereby the longitudinal side edges of each blade lie within the respective slots in said sleeve, with the opposed outside side faces of each blade abutting the longitudinal side faces of the slots in the outer sleeve, one blade being pivotally attached to one side of the outer sleeve adjacent one end of one slot therein and the other blade being pivotally attached to the other side of the outer sleeve adjacent the corresponding end of the other slot therein, a cam face for each blade at the end of the respective slot in the inner bar member adjacent the pivoted end of the blade, and a cam follower provided on each blade adjacent its pivoted end and engageable with a respective cam face whereby upon relative axial displacement of the outer sleeve and the inner bar member, each cam face is engaged by its respective cam follower and the blades are caused tO pivot simultaneously radially outwardly.
 4. The cutter bit as claimed in claim 1 in which said bar member and cutter blades are provided with complemental means, operative upon movement of the bar member in the opposite direction, to retract the cutter blades into the slots.
 5. The cutter bit as claimed in claim 2 in which said inner bar member and cutter blades are provided with complemental means operative, upon movement of the inner bar member in the opposite direction relative to the outer tubular member to retract the cutter blades into the apertures.
 6. A cutter bit including a walled outer sleeve having opposite ends, a cutter secured to one end, a bar member mounted within and capable of axial movement relative to the outer sleeve, said bar member being provided with at least two slots diametrically therethrough and elongated in the axial direction, with the slots being axially offset one from the other, said outer sleeve being provided with at least two pairs of diametrically opposed, axially extending slots respectively registering with said slots in the bar member, a cutter blade lying within each slot in the bar member, each blade being of a width not substantially less than the outside diameter of the sleeve whereby the longitudinal side edges of each blade lie within the respective slots in the sleeve, with the opposed outside side faces of each blade abutting the longitudinal side faces of the slot in the outer sleeve, one blade being pivotally attached to one side of the sleeve adjacent one end of one slot therein and the other blade being pivotally attached to the other side of the sleeve adjacent the corresponding end of the other slot therein, a cam face for each blade at the end of the respective slot in the bar member adjacent the pivoted end of the blade, a cam follower on each blade adjacent its pivoted end and engageable with a respective cam face, a cylinder for the opposite end of the outer sleeve, a piston in the cylinder movable longitudinally relative to the sleeve, spring means within the outer sleeve adjacent said one end thereof urging the bar member against the piston, means to introduce fluid pressure into the cylinder so that the piston displaces the bar member against the action of the spring means in a direction towards said one end of the sleeve whereby each cam face is engaged by its respective cam follower and the blades are caused to pivot simultaneously radially outwardly, each blade having an arcuate slot therein, and two pins extending outwardly from the bar member, with a pin located in each arcuate slot whereby upon cessation of the introduction of fluid pressure into the cylinder, the spring means urges the bar member towards the opposite end of the sleeve and said pins and arcuate slots cooperate to retract blades into the slots in the bar member. 